The present invention generally relates to avionic equipment and, more specifically, to an enhanced avionics tray assembly and seal assembly.
An avionic tray assembly provides support and self-indexing for rack mounted equipment, commonly known as line replaceable units (LRUs). Each LRU contains internal electrical components that are connected to the avionic tray assembly with a rack and panel connector and mechanical fasteners, commonly known as hold-downs. The rack and panel connector, located at the rear of the avionic tray assembly, provides the electrical connection to aircraft systems and structural support for the LRU. The hold-downs, located at the front of the avionic tray assembly, secure the LRU into the avionics tray assembly and apply horizontal force to engage the rack and panel connector. The avionic tray assembly also provides a cooling interface for the internal electrical components of the LRU. The cooling interface may be accomplished with a seal assembly that is part of the overall avionic tray assembly. The seal assembly is attached on the lower horizontal surface of the avionic tray assembly and contacts the lower surface of the LRU when it is fully installed. The hold-downs also provide a downward force that will compress the seal assembly against the LRU to complete the cooling interface.
The avionic tray assembly includes mounting provisions for an LRU, electrical wire bundle(s), and a cooling interface that can be adjusted to specific thermal requirements for each piece of equipment. The avionic tray assembly varies in width accommodating the specific size of each LRU based on standard increments, commonly known as Austin Trumbull Radio Racking System (ATR) or Modular Concept Unit (MCU). The LRU specifications for ATR and MCU, defined by Aeronautical Radio Incorporated (ARINC) 404A or ARINC 600, are industry standards for rack mounted aircraft avionic equipment. The term rack mounted equipment refers to LRUs that are installed on an avionic tray assembly, which are further attached to an assembly known as a shelf assembly. The shelf assembly may further be attached to a support structure known as a rack.
Typically, when an LRU is being Installed, it rotates around a horizontal axis, influenced by the orientation of the rack and panel connector. When the LRU rotates, it could contact an outside horizontal surface of the avionic tray assembly. If such contact occurs, the force required for engaging or disengaging the LRU from the rack and panel connector would increase. Since the hold-downs are force-limiting devices, the amount of horizontal force applied could be inadequate to fully mate or engage the LRU to the rack and panel connector. As such, the electrical contacts internal to the rack and panel connector may not be mated properly thus causing a loss of signal. If this occurs, the electrical circuit would be incomplete and the LRU would require removal and re-installation (known as re-racking) In order to function properly.
During maintenance activities, LRUs may be removed and unintentional pressure may be applied to the seal assembly in a downward direction. Such pressure can dislodge the seal assembly from the tray assembly. As such, the shelf assembly would need to be disassembled, reassembled and pressure tested prior to the airplane being returned to revenue service.
A conventional tray assembly, described, for example, in U.S. Pat. No. 4,458,296 and assigned to the assignee of the present invention, has several manufacturing concerns associated with its assembly process. For example, to install the seal assembly, an extruded seal may be press fit into location by deforming the extruded seal then smoothing it back to its original shape. The seal assembly can be installed Into the tray assembly with a sealant between the extruded seal and the tray detail. Additional sealant may then be applied on the periphery of the extruded seal to complete the installation process. The existing seal assembly has adhesion problems between the silicon extruded seal and the metering plate, and between the seal assembly and the tray detail.
A conventional seal assembly, also described, for example, in U.S. Pat. No. 4,458,296, may be fabricated from different materials. The metering plate detail can be formed using a semi-rigid-plastic while the extruded seal may be fabricated from an extruded silicon material before being cut to length. The extruded seal can be attached to a metering plate detail using an adhesive. Since the metering plate detail and the extruded seal are usually manufactured with different materials, the adhesion of the adhesive is less than satisfactory, typically resulting in rework prior to installation in the tray assembly.
Other limitations include an internal bend radius of the tray detail being lower than design standards specify. In such a scenario, a dye penetrate inspection is typically performed to insure part quality. Dye penetrate can highlight flaws and cracks In the tray assembly that are too small to see by normal visual inspection. Such inspections are costly and time consuming
As can be seen, there is a need for an improved tray assembly that improves LRU alignment and engagement characteristics, reduces the manual effort required during tray assembly, indexes the seal assembly to the tray assembly, increases the depth of the recessed area of the tray detail that receives the seal assembly, includes a plurality of metering plate detail index bosses, and increases the internal radius of the tray assembly.
In one aspect of the present invention, an avionics tray assembly comprises a seal assembly and a tray detail. The seal assembly comprises a metering plate detail, a plurality of tabs disposed along the metering plate detail, a plurality of location bosses disposed along the metering plate detail and, a flange extending from the metering plate detail, while the tray detail comprises a plurality of index bosses and a horizontal surface, wherein the plurality of index bosses receive the plurality of location bosses, wherein the plurality of tabs secure the seal assembly to the tray detail, and wherein the flange secures the seal assembly to the horizontal surface.
In another aspect of the present invention, an avionics tray assembly comprises a seal assembly and a tray detail. The seal assembly comprises a metering plate detail, a plurality of tabs disposed along the metering plate detail, a plurality of location bosses disposed along the metering plate detail, a flange extending from the metering plate detail, a top portion, an upper seal coupled to the top portion, a bottom portion, and a lower seal coupled to the bottom portion, while the tray detail comprises a plurality of index bosses, horizontal surface, at least one vertical surface, a recessed area, and an internal radius, wherein the internal radius supports an area of transition between the horizontal surface and the at least one vertical surface, wherein the recessed area further comprises a cutout; wherein the cutout receives the seal assembly, wherein the plurality of index bosses receive the plurality of location bosses, wherein the plurality of tabs secure the seal assembly to the tray detail, and wherein the flange secures the seal assembly to the horizontal surface.
In a further aspect of the present invention, a seal assembly comprises a metering plate detail, a plurality of tabs disposed along the metering plate detail, a plurality of location bosses disposed along the metering plate detail, a flange extending from the metering plate detail, and punch-out portions disposed along the metering plate detail, wherein aperture openings are formed through the metering plate detail in a location of the punch-out portions if the punch-out portions are removed.
In yet another aspect of the present invention, a seal assembly comprises a metering plate detail, a plurality of tabs disposed along the metering plate detail, a plurality of location bosses disposed along the metering plate detail, and a flange extending about 0.40 inches from the metering plate detail.
In yet a further aspect of the present invention, a seal assembly comprises a metering plate detail, a plurality of tabs disposed along the metering plate detail, a plurality of location bosses disposed along the metering plate detail, a flange extending from the metering plate detail, a top portion, an upper seal coupled to the top portion, a bottom portion, and a lower seal coupled to the bottom portion.
In yet a further aspect of the present invention, a method for producing a seal assembly comprises forming a metering plate detail, forming at least one tab on the metering plate detail, forming at least one index boss on the metering plate detail, forming at least one flange on the metering plate detail, forming a top portion, forming a bottom portion, forming at least one seal on the top portion, and forming at least one seal on the bottom portion.
In yet another aspect of the present invention, a tray detail comprises a horizontal surface, at least one vertical surface, a recessed area sunk to a minimum depth of about 0.05 inches, and an internal radius of about 0.07 inches supporting an area of transition between the horizontal surface and the at least one vertical surface.
In yet a further aspect of the present invention, a tray detail comprises a horizontal surface, two vertical surfaces, a recessed area disposed along the horizontal surface, the recessed area comprising a cutout, an index boss disposed along the cutout, and an internal radius supporting an area of transition between the horizontal surface and the two vertical surfaces.
In yet another aspect of the present invention, a method for producing a tray assembly comprises forming a horizontal surface, forming a plurality of vertical surfaces, forming a recessed area to a minimum depth of about 0.05 inches in a portion of the horizontal surface, forming a cutout through a portion of the recessed area, and forming an internal radius of about 0.07 inches along an area of transition between the horizontal surface and the vertical surfaces.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.